The horse’s diet is made up of a number of constituents from which energy can be derived, including Gross energy, Digestible energy, Metabolisable energy, and Net energy.

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Gross Energy (GE)
Describes the total energy contained within a feed. It is measured as the heat given off when the feed is burned in a bomb calorimeter.

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Digestible Energy (DE)
Digestible energy is the gross energy of a feed, minus the energy content of the faeces attributable to it. (Frape, 2004)

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Metabolisable Energy (ME)
The metabolisable energy of a food is the digestible energy less the energy lost in the urine and combustible gases.

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Net Energy (NE)
The deduction of the heat increment of food from its metabolisable energy gives the total of net energy value.
‘Heat increment’ – can be defined as the heat loss of a nourished animal in excess of that lost by a fasting animal. (Frape, 2004).

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Figure 1 below illustrates these terms.